> It is very likely that the reason the transistor failed was because of poor cooling, as it is a low cost, high-resistance transistor that is running near its design limits.
This wouldn't be my first guess based on that hole, which was formed more abruptly than a little overheating. Cooling the outside of the package is only going to buy a little more margin, not fix the root problem.
Looking at that schematic snippet, what is up with the capacitance on that gate drive circuit? They want a slower turn on to avoid a popping sound? Maybe it's a reference circuit that worked fine with a larger package or something, and a UF6 doesn't have enough thermal mass? If the turn on/off time is the problem, removing one of C489 or C530 could stop it from happening again.
Or it could be something downstream drawing too much power on that rail or shorting it out. Since you're replacing the part, you might as well just use a FET with a lower resistance and some hope to address this possibility.
FWIW some thinner flux (like a Kester 951) will generally let you fix solder bridges without starting all over.
I've commented elsewhere on the thread, but, this also has the potential to be destroyed by software. That AUDIO_PWR_EN appears to be a signal that can be controlled by software. If you switch it fast enough such that the MOSFET is kept mostly in the linear region (due to the RC on the gate), you can kill the MOSFET very quickly.
Yeah this looks like an SOA violation to me based on the hole. Usually you would turn a FET like that on slowly to avoid high inrush current into the downstream circuit, but ~10ms seems a bit silly. That would also explain why this escaped their initial testing because the FET wouldn't get hot in normal operation.
Although, if it's a 5V0 or 3V3 rail they may just not be turning on the FET enough. It's Rds(on) is high at ~3 V, and they divide down the gate drive to get reasonably symmetric on/off times and slow speed.
I basically came here to say the same, regarding the FET: Most likely there are parts with the same form factor but much lower resistance (both switching and fully on), which don't have that problem. The price-difference might matter in mass production, but for a repair at home, I don't see a reason to go with a cheap part.
Decreasing the turn on/off time might also be a good idea to prevent future repairs (nice spot!).
This wouldn't be my first guess based on that hole, which was formed more abruptly than a little overheating. Cooling the outside of the package is only going to buy a little more margin, not fix the root problem.
Looking at that schematic snippet, what is up with the capacitance on that gate drive circuit? They want a slower turn on to avoid a popping sound? Maybe it's a reference circuit that worked fine with a larger package or something, and a UF6 doesn't have enough thermal mass? If the turn on/off time is the problem, removing one of C489 or C530 could stop it from happening again.
Or it could be something downstream drawing too much power on that rail or shorting it out. Since you're replacing the part, you might as well just use a FET with a lower resistance and some hope to address this possibility.
FWIW some thinner flux (like a Kester 951) will generally let you fix solder bridges without starting all over.